Diseases of the nervous system / edited by Archibald Church.

Date:
1908
Catalogue details

Licence: In copyright

Credit: Diseases of the nervous system / edited by Archibald Church. Source: Wellcome Collection.

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    extends to the hemispheres of the cerebrum, the diencephalon or inter-brain with the thalamus opticus, the mesencephalon or mid-brain with the corpora quadrigemina, the metencephalon or after-brain with the cerebellum and pons, and the myelencephalon or cerebrospinal axis with the medulla oblongata. The telencephalon—above all, the pallium—from which the cerebrum of the vertebrate animals is formed, is the most highly developed of these divisions, and attains its mightiest conformation in man. While in vertebrate fish the simple epithelial covering is permanent, in man this finally covers to a sur- prising extent the entire brain. In the telencephalon the process is the same as in all other parts of the brain, the basal section becomes very thick while the dorsal portions are thin but become very broad. Hence, in the telen- cephalon, the closure of the medial wall of the hemispheres does not develop nervous elements but fills out the lateral ventricles as the choroid plexus. The communications of the cerebral cavities with the surface of the brain, which are at first free, are arrested toward the end of the fourth month by the development of the corpus callosum. Through this, as well as the fornix which lies below it, the two hemispheres of the cerebrum expand, while the anterior cerebral ganglia develop from the basal portion the so-called ground plate of the telencephalon, from the corpus striatum which is divided by the projection fibers which pass from the cortex through the internal capsule into the nucleus caudatus, and from the nucleus lentiformis to which the nucleus amygdalae and the claustrum are added. Owing to the adhesion of the corpus striatum to the thalamus opticus in the perfectly devel- oped brain the space between the telen- cephalon and diencephalon is hardly no- ticeable. Simultaneously with the formation of the different portions of the brain and the more or less greatly increased thick- ness of their walls, the original spaces in the cerebral vesicles develop into a ven- tricular system varying in extent and form. In accordance with the develop- ment of the hemispheres two ventricles form in the cerebrum; the lateral ven- tricle, which at first communicate with the surface, are subsequently shut off from it but communicate with each other by means of the foramen Monroi, through which also we pass to the third ventricle in the cavity of the diencephalon. The latter is limited laterally by the optic thalamus, and above by epithelium from the choroid plexus, while it passes down- ward in funnel shape into the infundibu- lum. Through the comparatively wide third ventricle we pass dorsally to the narrow aqueduct of Sylvius, the canal of the mesencephalon, the upper bounff- Fig. 2.—The Development of the Ven- tricular System. (After Welcker.) IV, Fourth ventricle; r.l., Recessus later- alis; a., Aquaeductus Sylvii; III, Third ventricle; F.M., Foramen Monroi; c.a., Cornu anterius; c.p., Cornu posterius; c.i.. Cornu inferius of the lateral ven- tricles; h., Pes hippocampi major.
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